Declare the erl_types:var_table() type as opaque

and do the following changes:
  in erl_types: export the type and an appropriate constructor for it
  in dialyzer_contracts: perform all necessary code modifications to
    fix all dialyzer warnings

Although no warnings are reported by dialyzer, it's quite possible that
these are not the only places where the opacity of the var_table() data
structure is violated. But I decided to leave these places for a better
version of dialyzer to discover...

2 files changed, 23 insertions, 9 deletions

diff --git a/lib/dialyzer/src/dialyzer_contracts.erl b/lib/dialyzer/src/dialyzer_contracts.erl
index 116260778c..d1ffa07706 100644
--- a/lib/dialyzer/src/dialyzer_contracts.erl
+++ b/lib/dialyzer/src/dialyzer_contracts.erl
@@ -479,7 +479,8 @@ initialize_constraints([], _MFA, _RecDict, _ExpTypes, _AllRecords, Acc) ->
 initialize_constraints([Constr|Rest], MFA, RecDict, ExpTypes, AllRecords, Acc) ->
   case Constr of
     {type, _, constraint, [{atom, _, is_subtype}, [Type1, Type2]]} ->
-      T1 = final_form(Type1, ExpTypes, MFA, AllRecords, maps:new()),
+      VarTable = erl_types:var_table__new(),
+      T1 = final_form(Type1, ExpTypes, MFA, AllRecords, VarTable),
       Entry = {T1, Type2},
       initialize_constraints(Rest, MFA, RecDict, ExpTypes, AllRecords, [Entry|Acc]);
     {type, _, constraint, [{atom,_,Name}, List]} ->
@@ -489,8 +490,9 @@ initialize_constraints([Constr|Rest], MFA, RecDict, ExpTypes, AllRecords, Acc) -
   end.
 
 constraints_fixpoint(Constrs, MFA, RecDict, ExpTypes, AllRecords) ->
+  VarTable = erl_types:var_table__new(),
   VarDict =
-    constraints_to_dict(Constrs, MFA, RecDict, ExpTypes, AllRecords, maps:new()),
+    constraints_to_dict(Constrs, MFA, RecDict, ExpTypes, AllRecords, VarTable),
   constraints_fixpoint(VarDict, MFA, Constrs, RecDict, ExpTypes, AllRecords).
 
 constraints_fixpoint(OldVarDict, MFA, Constrs, RecDict, ExpTypes, AllRecords) ->
@@ -498,11 +500,11 @@ constraints_fixpoint(OldVarDict, MFA, Constrs, RecDict, ExpTypes, AllRecords) ->
     constraints_to_dict(Constrs, MFA, RecDict, ExpTypes, AllRecords, OldVarDict),
   case NewVarDict of
     OldVarDict ->
-      DictFold =
+      Fun =
 	fun(Key, Value, Acc) ->
 	    [{subtype, erl_types:t_var(Key), Value}|Acc]
 	end,
-      FinalConstrs = maps:fold(DictFold, [], NewVarDict),
+      FinalConstrs = maps:fold(Fun, [], NewVarDict),
       {FinalConstrs, NewVarDict};
     _Other ->
       constraints_fixpoint(NewVarDict, MFA, Constrs, RecDict, ExpTypes, AllRecords)
@@ -512,12 +514,12 @@ final_form(Form, ExpTypes, MFA, AllRecords, VarDict) ->
   from_form_with_check(Form, ExpTypes, MFA, AllRecords, VarDict).
 
 from_form_with_check(Form, ExpTypes, MFA, AllRecords) ->
-  from_form_with_check(Form, ExpTypes, MFA, AllRecords, maps:new()).
+  VarTable = erl_types:var_table__new(),
+  from_form_with_check(Form, ExpTypes, MFA, AllRecords, VarTable).
 
 from_form_with_check(Form, ExpTypes, MFA, AllRecords, VarDict) ->
   Site = {spec, MFA},
-  erl_types:t_check_record_fields(Form, ExpTypes, Site, AllRecords,
-                                  VarDict),
+  erl_types:t_check_record_fields(Form, ExpTypes, Site, AllRecords, VarDict),
   erl_types:t_from_form(Form, ExpTypes, Site, AllRecords, VarDict).
 
 constraints_to_dict(Constrs, MFA, RecDict, ExpTypes, AllRecords, VarDict) ->
diff --git a/lib/hipe/cerl/erl_types.erl b/lib/hipe/cerl/erl_types.erl
index 84addcc105..b037a4360c 100644
--- a/lib/hipe/cerl/erl_types.erl
+++ b/lib/hipe/cerl/erl_types.erl
@@ -220,6 +220,7 @@
          is_opaque_type/2,
 	 is_erl_type/1,
 	 atom_to_string/1,
+	 var_table__new/0,
 	 map_pairwise_merge/3
 	]).
 
@@ -236,7 +237,7 @@
 -export([t_is_identifier/1]).
 -endif.
 
--export_type([erl_type/0, opaques/0, type_table/0]).
+-export_type([erl_type/0, opaques/0, type_table/0, var_table/0]).
 
 %%-define(DEBUG, true).
 
@@ -380,7 +381,7 @@
 -type type_table() :: dict:dict(record_key() | type_key(),
                                 record_value() | type_value()).
 
--type var_table() :: #{atom() => erl_type()}.
+-opaque var_table() :: #{atom() => erl_type()}.
 
 %%-----------------------------------------------------------------------------
 %% Unions
@@ -5464,6 +5465,17 @@ family(L) ->
   sofs:to_external(F).
 
 %%=============================================================================
+%%
+%% Interface functions for abstract data types defined in this module
+%%
+%%=============================================================================
+
+-spec var_table__new() -> var_table().
+
+var_table__new() ->
+  maps:new().
+
+%%=============================================================================
 %% Consistency-testing function(s) below
 %%=============================================================================